1. Field of the Invention
The present invention relates to a reagent dispenser head, and particularly to a dispenser head with a piezoelectric actuator which dispenses reagents and other chemical solutions through a nozzle plate in droplets.
2. Description of the Related Art
It is frequently desirable to coat a surface or membrane with drops of a chemical or reagent material forming an image or pattern. Typical applications for this technology include test strips used for medical diagnostics, microarrays, xe2x80x9clab on a chipxe2x80x9d, etc. Current technology uses dispensing systems having one hundred twenty-eight or more separate droplet actuators arranged in the desired image pattern and/or devices with motion control systems to move single droplet actuators in the desired image pattern. The problem with such devices is that the separate actuator systems render it difficult to achieve uniformity in droplet size, and while many advances have been achieved in motion control systems, it is often difficult to achieve both accuracy and precision in replicating images faithfully. In addition, these systems tend to be complex and expensive due to the duplication of components and the cost and expense of electronic control systems. The present invention overcomes the difficulties of prior art systems through a reagent dispensing head having a piezoelectric actuator (preferably a bimorph), a single nozzle plate having a plurality of orifices defining an image pattern, and a capillary fluid feed system disposed between the piezoelectric actuator and the nozzle plate. A control system generates a single pulse for actuating the piezoelectric element.
Known devices for dispensing fluid droplets using a single piezoelectric actuator, a single fluid chamber, and a single orifice or nozzle for each droplet include U.S. Pat. No. 3,683,212, issued Aug. 8, 1972 to S. I. Zoltan (tubular ceramic piezoelectric transducer expanding and contracting radially to eject fluid quantity proportional to voltage rise time); U.S. Pat. No. 4,877,745, issued Oct. 31, 1989 to Hayes et al. (plurality of jet heads for dispensing reagents into cells or printing test strips or ink onto paper, each jet head having a separate tubular piezoelectric transducer and a separate orifice); and U.S. Pat. No. 5,483,469, issued Jan. 9, 1996 to Van den Engh et al. (cytometer having a fluid flow chamber with a single orifice and a piezoelectric crystal for creating a single steady flow of drops).
Several inkjet printing devices are of this variety, representative patents including U.S. Pat. No. 5,854,645, issued Dec. 29, 1998 to Witteveen et al. (inkjet area with plurality of ink chambers); U.S. Pat. No. 5,971,528, issued Oct. 26, 1999 to M. Yoshimura (plurality of ink jet channels formed by piezoelectric walls); and U.S. Pat. No. 4,700,203, issued Oct. 13, 1987 to Yamamura et al. (ink jet head including some embodiments having a bimorh actuator).
Several devices for delivering measured or metered doses of medications or other fluids use piezoelectric transducers, often vibrating at the crystal""s resonant frequency. Representative examples include U.S. Pat. No. 5,487,378, issued Jan. 1, 1996 to Robertson et al. (inhaler with a conically shaped port with a nozzle having a plurality of holes and a piezoelectric disc vibrating at the resonant frequency); U.S. Pat. No. 5,518,179, issued May 21, 1996 (atomizer with membrane having multiple perforations and piezoelectric transducer attached directly to membrane); U.S. Pat. No. 5,838,350, issued Nov. 17, 1998 to Newcombe et al. (cylindrical transducer and perforated membrane which vibrates); German Patent No. 2,915,851, published Oct. 30, 1980 (cylindrical piezoelectric transducer with jet formed by glass capillary tube and having circuitry for ejecting measured quantity of fluids); and U.K. Patent No. 2,240,494, published Aug. 7, 1991 (atomizer with membrane having plurality of holes and piezoelectric transducer indirectly connected to the membrane in order to vibrate the membrane).
Other relevant devices are described in U.S. Pat. No. 6,001,309, issued Dec. 14, 1999 to Gamble et al. (device for creating an array of microspots for laboratory screening and assays which has a plurality of jet devices moved as a group); U.S. Pat. No. 6,063,339, issued May 16, 2000 to Tisone et al. (device for precisely dispensing dots of reagents onto test strips, test arrays, well plates, etc., including a dispensing head, a pump device and a controller for moving the dispensing head and/or table in the X, X-Y, or X-Y-Z directions); U.S. Pat. No. 4,530,464, issued to Yamamoto et al on Jul. 23, 1985 (annular piezoelectric transducer with nozzle plate having a plurality of holes fixedly attached to the transducer); and U.S. Pat. Nos. 4,533,082 and 4,605,167 issued to Maehara et al. and N. Maehara on Aug. 6, 1985 and Aug. 12, 1986, respectively (ring-shaped piezoelectric transducer with nozzle plate having one or more holes therein bonded to transducer and vibrating at resonant frequency).
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a reagent dispenser head solving the aforementioned problems is desired.
The reagent dispenser head has a piezoelectric actuator supported by a back plate, a front plate having a conical well and a fluid inlet connected by a shallow channel, and a thin, impermeable membrane disposed between the piezoelectric actuator and the spherical well. The well has a window defined therein opening on a nozzle plate having an array of orifices which are arranged to define a predetermined image or pattern. The dispenser head is supplied with a reagent or other liquid through the fluid inlet, the fluid feeding into the well through the channel. A control system is connected to the piezoelectric actuator to provide an electrical pulse or trigger which causes the piezoelectric actuator to bend or deform, contracting the depth of the well and ejecting drops of reagent through all the orifices simultaneously, coating a substrate with reagent in the image pattern.
The reagent dispenser head is most useful in laboratory applications, such as medical diagnostics, microarrays, lab on a chip, etc. The reagent dispenser head may be used in the preparation of indicator strips. The reagent dispenser head eliminates the need for multiple dispensing heads and motion control systems to dispense droplets in a pattern by means of the single nozzle plate with multiple orifices in the desired pattern, resulting in significant cost reduction. The use of a single piezoelectric actuator and control signal helps to ensure that the image pattern may be reproduced with precision and accuracy.
Accordingly, it is a principal object of the invention to provide a reagent dispenser head which dispenses multiple drops of a reagent simultaneously in a predetermined image pattern.
It is another object of the invention to dispense multiple drops of reagent in a predetermined image pattern with a single control signal in order to improve reproducibility of the image by eliminating irregularities in timing of multiple control signals.
It is a further object of the invention to dispense multiple drops of reagent in a predetermined image pattern without the necessity of a motion control system for movement of the dispensers head, thereby avoiding irregularities produced by variations in mechanical tolerances and mechanical degradation of the motion control system.
Still another object of the invention is to provide a reagent dispenser head for dispensing multiple drops of reagent in a predetermined image pattern with few moving parts.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.